1. Field of the Invention
This invention relates to devices which rely on the Inverse Wiedemann Effect, which devices may be employed in a number of applications, such as voltage generators and magnetic memory devices.
2. The Prior Art
For many years, the so-called Wiedemann Effect has been well known. The Wiedemann Effect is the resulting twist produced in a wire that exhibits magnetostriction when the wire is placed in a longitudinal magnetic field and has an electric current flowing therethrough. The converse or inverse of this phenomenon has also been long recognized and is commonly called the Inverse Wiedemann Effect. In the Inverse Wiedemann Effect, axial magnetization is produced by a magnetostrictive wire that carries current therethrough when the wire is twisted.
There have been a number of attempts to employ the Wiedemann and Inverse Wiedemann Effects in practical applications. Such attempts are discussed at length in an article by J. A. Granath entitled Instrumentation Applications of Inverse Wiedemann Efffect which appeared in the Journal of Applied Physics, Vol. 31, pp. 178S - 180S (May, 1961) and in a publication by The International Nickel Company, Inc. of New York, New York entitled Magnetostriction. At least two U.S. patents disclose devices reupon the Inverse Wiedemann Effect, namely, U.S. Patent No. 2,511,178 granted to H. C. Roters on June 12, 1950, and U.S. Patent No. 3,083,353 granted to A. H. Bobeck on Mar. 26, 1963. In the Roters patent, devices are disclosed which rely upon a central core or rod of magnetostrictive material that exhibits a substantially linear, non-hysteretic magnetic induction (B) versus twist ( .alpha. ) curve. The reliance on such a material yields a significant limitation in the achievable rate of change of the axial magnetic field produced by twisting magnetostrictive element, whereby to limit the practical voltage output of such devices. The devices described by Bobeck in his aforementioned patent do not vary the amount of twist on the magnetostrictive element, but rely on the interrelationship of a fixedly twisted magnetostrictive element and magnetic fields induced by current flowing through that element and by current flowing through conductive coils surrounding discrete portions of the element.